So went the disclaimer back in October 2010 as British pepper aficionado Leo Scott and his friend Lok Chi uploaded a video of themselves eating a new variety, the Naga Viper, developed by fellow grower Gerald Fowler. The warning was warranted as the two very experienced chiliheads sweated, writhed in pain and briefly lost the ability to speak after each chewing and swallowing one of the bright-red capsicums.

Hot Hot Hot!

A month later, the Guinness Book of World Records certified what Mr. Scott found out the hard way: The Naga Viper was the hottest pepper ever grown, measuring 1.382 million Scoville Heat Units, the standard measure of heat. That is 225 times as hot as a jalapeño can sometimes be.

Unfortunately for Mr. Fowler, his record wouldn't stand for long. Four months later, the Naga was dethroned by the Trinidad Scorpion Butch T, the current record holder, at 1.464 million Scovilles.

"I was shocked," says Mr. Scott, who lives near Bristol, England. "You've got this global community of chili growers who are competing ruthlessly with each other."

The Naga itself had just surpassed the Infinity Chili, which held the official record for a mere eight months.

Alex de Wit, who co-owns the Chilli Factory in Morisset, Australia, with his brother Marcel, is one of the evil geniuses behind the Butch T. The trick, besides some nifty breeding by Australia's Hippy Seed Co., is specially enriched soil. He says "worm poop" is one of his secret weapons. He plans to submit to Guinness another batch of Butch T peppers being grown in tropical Queensland. He estimates that the more favorable growing conditions could add 10% to their potency.

Such one-upmanship raises the question of how many people can actually appreciate the march toward new heights of heat. Though he consumes chilis regularly, Mr. de Wit just once managed to eat half of one of his latest creations.

"After 800,000 Scoville units, you've got to be careful," he warns. "You'll pay the consequences—you'll be on the floor for hours. We've had people go to the hospital."

ENLARGE

The Red Savina Habanero was a heat leader in 1994 with 570,000 Scovilles.
Chile Pepper Institute

Luckily there is no record of anyone dying from eating peppers, according to Paul Bosland, head of New Mexico State University's Chile Pepper Institute, in Las Cruces, New Mexico. Known as "the chileman," Mr. Bosland deserves a large part of the credit for the current craze. Until the early 1990s, only two peppers had reached the 350,000 Scoville mark—the habanero and the Scotch bonnet. A hybrid variety called the Red Savina Habanero claimed the Guinness crown in 1994 with 570,000 Scovilles. That was believed to be about the upper limit of hotness for more than a decade.

Then Mr. Bosland was told of the Bhut Jolokia, or ghost pepper, a variety grown in remote Assam, India, that was being studied by the Indian army for use in grenades. Skeptical, Mr. Bosland got some seeds and was astonished to find that the peppers he grew averaged more than one million Scovilles, as measured by high performance liquid chromatography.

"Once we did that, it kind of opened the floodgates," he says.

Mr. Bosland claims to have broken the two million Scoville mark in February 2012 with his Trinidad Moruga Scorpion. That is the same strength as police-grade pepper spray—a substance no sensible person would let travel through his digestive tract. Mr. Bosland hasn't yet submitted paperwork to Guinness for the official record, and his claim really burns up Mr. de Wit, who insists his pepper is still the hottest. Only chemical chromatography that measures several samples for their average level of capsaicin, the chemical that gives peppers their bite, can establish a record claim. But Mr. Scott, one of the few people on Earth who has tasted both varieties, says the Moruga Scorpion is clearly hotter.

ENLARGE

Trinidad Scorpion Butch T pepper

"It was amazing," he says. "The heat was absolutely insane."

Mr. Bosland says that new records are mainly of interest as publicity for purveyors of sauces, which he isn't. But sauce producers haven't bothered to wait for Mother Nature to deliver hotter concoctions by adding potent extracts. Mr. Scott's friend, Nick Moore, proprietor of Dr. Burnörium's Hot Sauce Emporium in Bristol, is about to launch one called Psycho Serum weighing in at a scorching 6.4 million Scovilles. He compares its kick to "licking the surface of the sun."

The undisputed king of the hot sauce world though is Blair Lazar, a New Jersey entrepreneur who achieved a Guinness record of 16 million Scovilles—the scientific maximum. He required customers to sign a waiver before buying his "Blair's 16 Million Reserve." It consists of individual crystals of pure capsaicin produced in a laboratory.

Mr. Lazar started his business in 1989 when he was a bartender trying to clear out late-night stragglers. If they could eat wings doused with his original Death Sauce, they could stay. None could. But he says appreciation for spicy foods has grown immensely.

"When I started, no one knew what a habanero was—now it's a flavor of Doritos," he says. "No one knew what a chipotle was—now it's a fast-food chain."

Interest in all things spicy has been further stoked by the recent string of records, says Mr. Moore. "It all went a bit weird over the last 18 months or so," he says.

Some of his customers—mostly male—visit his shop to buy sauces or dried chilis on a dare. But many regulars are hooked on the sensation they get after eating them. Because it activates pain receptors, capsaicin releases pleasure chemicals called endorphins. Messrs. Moore, Scott and Lazar all say they have hot sauce with every meal.

For a natural high, though, superhot chilis require unnatural care to process, because they are an irritant. "Once you break them open, you have to be very, very careful," says Mr. Bosland. "We put on almost a hazmat suit—full body coveralls, a breathing apparatus and a hat."

And the arms race continues. With the rising interest, Mr. Scott expects to be sampling ever-hotter varieties in the future. "At the moment, I don't see a limit," he says.

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